1. Field of the Invention
The present invention relates to the off throttle steering response of jet pump propelled recreational watercraft. In particular, the invention relates to the deployment dynamics and control of a retractable rudder system to aid in the steering of recreational watercraft during off throttle or loss of power conditions.
2. Description of the Related Art
Water jet propelled recreational watercraft are very popular and are in use by large numbers of people throughout the world. These watercraft have become increasingly more powerful and capable of high speeds. The high speed capability inevitably leads to a requirement to avoid collisions, but the collision avoidance capability of these craft is severely hampered when the throttle is suddenly shut off, as might be the case when a pilot senses an imminent collision. Because these craft use a directed water jet to steer, shutting down the throttle can cause a lack of control, and create a collision in response to the same action taken to avoid it.
What is needed is a steering system to augment the jet propulsion system for the closed throttle condition. It would be of interest to have a system that not only responds to a closed throttle condition combined with full steering lock, but also has an anticipatory capability that senses steering rates and acceleration of steering rates to deploy the auxiliary system before lock is reached. In addition, it would be of interest to be able to deploy the steering system at a rate which is dependent on the speed of the craft, to avoid deploying devices at high craft speed that can cause unstable handling behaviors.
A retractable rudder system for water jet pump vessels is disclosed including at least one rudder pivotally disposed to rotate between a retracted position and a deployed position. A control means responsive to a throttle state condition, an immersion condition, and a steering condition is operative to generate an actuator control signal when the three conditions have predetermined states. An actuator means responsive to the control signal is operative to cause the rudder to rotate from the retracted position to the deployed position.
The invention discloses a retractable rudder device attached to the water jet nozzle of a watercraft. In a non-deployed condition, the rudders are latched in position and completely out of the water stream underneath the craft. When deployed, two rudders aligned with the axis of the steering nozzle, are rotated into position via springs and cables. The rudders pivot independently of each other, and will retract if contact with an underwater object is made or the craft is beached. A cable system connected to a control unit lowers the rudders into the deploy position. The cable system is actuated by a hydraulic cylinder using fluid pressure from the jet pump. The deployment rate can be varied by altering the fluid pressure in the hydraulic cylinder, and is a function of boat speed.
Deployment of the retractable rudder system is determined by an electronic control system. Input variables such as steering rates, jet pump pressure, throttle position, engine operation, immersion of the craft in the water determine if the rudder system is deployed. An anticipatory steering module is included in the controller to provide dynamic steering conditions under which the rudder system is deployed prior to full lock.